Various problems present themselves in design of current inkjet printers. Modern inkjet printers print at very high resolution, for example, 600 or even 1200 dots-per-inch (DPI). As resolution increases, droplet size typically decreases. With increased resolution and decreased dot size, it becomes more important that the pens be precisely located in the carriage. To accomplish accurate positioning of the pen in the carriage, the pen typically has a set of physical X, Y, and Z datums that are seated against a corresponding set of datums in the carriage stall.
Modern inkjet printers typically print in color and have a plurality of color pens, usually printing in cyan, magenta, yellow, and black. It is often desirable to provide a different pen for each color, so that if a single pen goes bad, only that pen need be replaced. However, each pen must be precisely aligned with the other colors, or the print quality of the printed images will be degraded. Therefore, the system must not only accommodate precision placement of the pens in the stalls, but precise alignment among the colors.
In addition to the mechanical positioning of the pens within the carriage, the pens must be fluidically connected to trailing tubes. The pens usually interface with some type of valve on the ends of the tubes. The pens make connection with these valves when they are inserted into the carriage stall. However, if the pen and valve interface is not correctly designed, the forces exerted on the pen during fluid interconnection will counteract the precision positioning of the datums, resulting in the pens being misaligned. The fluid interconnection mechanism must be designed so as to not act against the precise positioning resulting from the interaction of the datums.
Recent advances in printhead construction have allowed printheads to be designed to be a permanent or semi-permanent part of the printer, with separate ink cartridges that are fluidically connected in some fashion to the printhead.
Although the pens are preferably a permanent fixture in the printer, rather than being disposable, it is likely that many such pens will fail before the end of the life of the printer. Therefore, some provision must be made so that the pen can be removed and replaced with a new one. The mechanical datum system and fluid interconnect must also allow the new pen to be reliably and precisely positioned during such replacement. The system would be preferably designed so that installation and subsequent replacements could be done by a purchaser or by a field repair person away from factory conditions.
The invention provides an inkjet printing mechanism designed to receive an ink jet pen having a needle and a shroud surrounding the needle, the shroud attached to the pen by means of a neck, the pen also having pen datums configured for positioning the pen within a printer carriage. The printer includes a printer chassis and a media movement mechanism mounted to the chassis and constructed to position a print medium in a print zone. A carriage is mounted to the chassis and is constructed to receive the pen and to position the pen over the print zone. The carriage has a notch configured to receive the neck when the stall receives the pen. A valve is movably attached to the carriage and is configured to move with respect to the carriage to be received by the shroud when the notch receives the neck. A septum is positioned on the valve and configured such that when the valve is received by the shroud, the septum is pierced by the needle. A set of carriage datums is formed in the stall and configured to interface with the pen datums. A latching mechanism is associated with the carriage and constructed to seat the pen datums against the carriage datums to finely position the pen with respect to the carriage.
The invention also provides a method of installing an inkjet pen into a carriage of an inkjet printing mechanism. The method includes the steps of: placing the pen in a stall of the carriage to guide a neck on the pen into a notch formed in the carriage; moving the pen further into the stall and by means of registration of the pen with walls of the pen stall, guiding a shroud on the pen over a valve; urging the pen further into the stall until pen datums formed on the pen come into contact with carriage datums formed in the stall; and seating the pen datums against carriage datums to finely position the pen within the carriage;
The invention thus provides for reliable insertion of inkjet pens within their respective carriage stalls, with successive guiding mechanisms for aligning various parts of the pen with corresponding parts of the carriage. The invention allows for installation or replacements of pens to be reliably and easily done by a purchaser or by a field repair person away from factory conditions.
According to a second aspect of the present invention, there is provided a printer in which an inkjet printhead may be primed without removing the printhead from a carriage of the printer, the printer comprising a source of gas capable of delivering a predetermined controlled volume of gas at a pressure above ambient pressure, a carriage for holding at least one printhead and having coupling means for coupling a vent on the printhead to the source of gas, and a controller for controlling the priming of a printhead by the application of a controlled predetermined volume of gas to a printhead mounted in the carriage.
In a presently preferred embodiment of the invention a unitary latching device is provided which moves between an open position allowing individual inkjet print cartridges to be installed, removed or replaced and a closed position securely positioning a plurality of the print cartridges in a carriage during printing, replenishming and servicing modes. The latching device may include a pivotally mounted cover having individually spring loaded bars which protrude downwardly to engage a crown portion of the print cartridge and provide vector forces which hold positional datums on the print cartridge against matching datum surfaces on the carriage.
When the latching device is in closed position, the plurality of print cartridges are collectively held in the carriage in a manner which prevents manual interference in order to accomplish the following functions: printing as a result of a secure electrical interconnect contact through conductive pads on a print cartridge; ink replenishment as a result of a secure fluid interconnect between a reservoir inside the print cartridge and an external ink supply; and servicing of the printhead. In one embodiment such printhead servicing includes priming the print cartridge through air conduits in the cover which are in aligned engagement with a vent in the printhead when the latching device is in closed position.
The latching device can be manually disengaged in order to be moved from the closed position to an open position which allows easy access to each of the plurality of print cartridges for purposes of removal and replacement.